1. Field of the Invention
This invention relates to a multi-layered thin film heat transfer gauge for determining heat flow into an object by measuring the temperature gradient across a thin, heat resistive film with resistance thermometers having metallic thin film elements. More particularly, the invention relates to a heat transfer gauge made of thin films overlaid one over the other and adapted to measure heat flux of long duration at high spatial resolution with quick response.
2. Description of the Prior Art
A conventional heat transmission gauge of the thin film type, for instance that which has been used fairly frequently for measurements concerning shock wave tubes, has a heat-insulating substrate made of PYREX or the like and metallic thin films deposited on the substrate so as to form a resistance thermometer. The conventional heat transfer gauge of this type measures the transient and non-steady surface temperature rise of an object caused by an input heat flux, and the heat flux at the surface of the object is determined from the thus measured temperature rise by calculation. This heat transfer gauge using thin films has been practically the only one which has a high spatial resolution and quick response.
The conventional heat transfer gauge using thin films, however, has a shortcoming in that, since its principle of measuring the heat flux is based on the transient temperature rise of the surface of a heat-insulating thermally non-conductive substrate, it is applicable only to the measurement of that heat flux which is produced in a wind tunnel with short flow duration. If such conventional heat transfer gauge is applied to the measurement of heat flux in a supersonic or low-speed wind tunnel with long flow duration, the surface temperature of the object being tested is raised quickly and the conditions of constant-temperature wall are not satisfied, so that it cannot measure the steady state heat flux which is indispensable for heat flux measurement in such wind tunnels.
Thus, the conventional heat transfer gauge of the thin film type has been considered as the only heat flux sensor having a high spatial resolution and a quick response, but it has a shortcoming in that it is applicable only to the measurement of heat flux in a shock wave tube or other wind tunnels with short flow duration, so that its scope of application is rather limited. In fact there is no heat flux sensor with a high spatial resolution and a quick response which is applicable to the measurement of heat flux in a wind tunnel with long flow duration.
On the other hand, the study of heat transfer to the surface of an object has become very important in the technical fields of aeronautical engineering, space engineering, and like, especially in the research related to supersonic flight, re-entry to atmosphere, gas flow in prime movers, etc. In the problems of the above-mentioned study, a shift of spatial position on a very minute scale results in a large change of heat flux, so that the heat flux variation in such study is very difficult to measure, if not impossible, by the conventional heat transfer gauge of the thin film type. Accordingly, the phenomenon of local heat transfer inherent to the problems of the above study have been left unclear.
Thus, another disadvantage of the conventional heat transfer gauge of the thin film type is in that it is applicable only to a comparatively narrowly limited technical field.